Vaccine Original Antigenic Sin

About Vaccine Original Antigenic Sin

Original antigenic sin, a term coined by Thomas Francis Jr in 1960, describes the immune systems tendency to respond to familiar viral strains rather than new strains. When a person is exposed to a new variant after prior infection or vaccination, the immune system may produce antibodies to the original strain rather than the new variant. This phenomenon has been observed with influenza and is a concern for COVID boosters. The first influenza strain a person encounters shapes their lifetime immune response to flu. Original antigenic sin complicates vaccine design. Universal flu vaccines targeting conserved proteins aim to overcome this limitation. The concept has been debated and refined. Some researchers prefer the term immune imprinting to describe the phenomenon. The COVID pandemic demonstrated that prior infection or vaccination influences responses to new variants, though the clinical significance remains debated.